Grain-oriented electrical steel sheets are soft magnetic materials that used in iron cores for transformers, generators, and the like, and that have crystalline structures in which the <001> orientation, which is an easy magnetization axis of iron, highly accords with the rolling direction of the steel sheets. Such a crystalline structure (texture) is formed through secondary recrystallization such that coarse crystal grains with the (110)[001] orientation, or so-called Goss orientation, are caused to grow preferentially during secondary recrystallization annealing in the production of a grain-oriented electrical steel sheet.
Conventionally, such grain-oriented electrical steel sheets are manufactured by the following procedure (for example, U.S. Pat. No. 1,965,559A [PTL 1], JPS4015644B [PTL 2], and JPS5113469B [PTL 3]).
Specifically, a slab that contains about 4.5 mass % or less of Si and inhibitor components, such as MnS, MnSe, AlN, and the like is heated above 1300° C. to dissolve the inhibitor components, and then hot rolled into a hot rolled sheet. The hot rolled sheet is optionally subjected to hot band annealing. The hot rolled sheet is subjected to cold rolling either once, or twice or more with intermediate annealing performed therebetween, to obtain a cold rolled sheet having a final thickness. Then, for primary recrystallization and decarburization, the cold rolled sheet is subjected to decarburization and primary recrystallization annealing in a wet hydrogen atmosphere. Subsequently, after an annealing separator mainly composed of magnesia (MgO) being applied to a surface of the obtained steel sheet, the steel sheet is subjected to final annealing at 1200° C. for about 5 h for the purpose of secondary recrystallization and purification of the inhibitor components, to thereby obtain a product steel sheet.